Perpendicular magnetic recording medium and method for manufacturing the same

Abstract

A magnetic recording medium includes a magnetic recording layer composed of an L10 type ordered alloy at a low temperature. The magnetic recording layer of the L10 type ordered alloy exhibits high magnetic anisotropy energy Ku that is necessary for compatibility between improvement in thermal stability and reduction of noises. Specifically, the recording medium includes a nonmagnetic substrate, a nonmagnetic underlayer, a magnetic recording layer, a protective layer, and a liquid lubricant layer sequentially formed on the substrate. The magnetic recording layer is formed by alternately depositing an iron or cobalt layer having thickness in a range of 0.1 nm to 0.3 nm and a platinum layer having thickness of in a range of 0.15 nm to 0.35 nm repetitively. The magnetic recording layer is mainly composed of an alloy of FePt or CoPt that includes a region with an L10 type ordered structure.

What is claimed is:  
     
         1 . A perpendicular magnetic recording medium comprising a nonmagnetic substrate and layers laminated sequentially on the substrate, the layers including a nonmagnetic underlayer, a magnetic recording layer, a protective layer, and a liquid lubricant layer, wherein the magnetic recording layer is formed by alternately laminating an iron or cobalt layer having thickness in a range of 0.1 nm to 0.3 nm and a platinum layer having thickness in a range of 0.15 nm to 0.35 nm repetitively, and is mainly composed of an alloy of FePt or CoPt including a region of L10 type ordered lattice.  
     
     
         2 . A perpendicular magnetic recording medium according to  claim 1 , wherein a thickness of the magnetic recording layer is in a range of 3 nm to 15 nm.  
     
     
         3 . A perpendicular magnetic recording medium according to  claim 1 , wherein a (001) crystal lattice plane in the region of L10 type ordered lattice is formed in parallel to a surface of the magnetic recording layer.  
     
     
         4 . A perpendicular magnetic recording medium according to  claim 1 , wherein the underlayer is composed of a metal being selected from a group consisting of Ag, Al, Au, Cu, Ir, Ni, Pt, and Pd, or an alloy mainly composed of at least one metal selected from the group consisting of Ag, Al, Au, Cu, Ir, Ni, Pt, and Pd, or the underlayer is composed of chromium or chromium alloy.  
     
     
         5 . A perpendicular magnetic recording medium according to  claim 1 , wherein the underlayer has a thickness in a range of 5 nm to 50 nm.  
     
     
         6 . A perpendicular magnetic recording medium according to  claim 1  further comprising a nonmagnetic seed layer between the substrate and the underlayer, wherein the seed layer is composed of MgO, NiO, TiO, or titanium carbide or titanium nitride, and a dominant crystal alignment plane of the seed layer is (100) plane.  
     
     
         7 . A perpendicular magnetic recording medium according to  claim 6 , wherein the seed layer has a thickness in a range of 3 nm to 15 nm.  
     
     
         8 . A perpendicular magnetic recording medium according to  claim 1 , wherein the substrate is selected from a group consisting of an aluminum substrate, a silicon wafer with an oxidized surface, a fused quartz substrate, a glass substrate, and a plastic resin substrate.  
     
     
         9 . A perpendicular magnetic recording medium according to  claim 1 , wherein perpendicular magnetic anisotropy energy Ku of the magnetic recording layer is in a range of 7×10 5  J/m 3  to 7×10 6  J/m 3 .  
     
     
         10 . A perpendicular magnetic recording medium according to  claim 1 , wherein the magnetic recording layer is formed by means of a DC magnetron sputtering method.  
     
     
         11 . A method for manufacturing a perpendicular magnetic recording medium comprising: 
 preparing a nonmagnetic substrate;    forming a nonmagnetic underlayer on the substrate;    forming a magnetic recording layer mainly composed of an alloy comprising FePt or CoPt including a region of L10 type ordered lattice on the underlayer by laminating alternately an iron or cobalt layer having thickness in a range of 0.1 nm to 0.3 nm and a platinum layer having thickness in a range of 0.15 nm to 0.35 nm, repetitively; and    forming a protective layer on the magnetic recording layer, and forming a liquid lubricant layer on the protective layer.    
     
     
         12 . A method for manufacturing a perpendicular magnetic recording medium according to  claim 11 , wherein the magnetic recording layer is formed by means of a DC magnetron sputtering method.  
     
     
         13 . A method for manufacturing a perpendicular magnetic recording medium according to  claim 11  further comprising a step of heating at a temperature lower or equal to 400° C. after the step of forming the magnetic recording layer.  
     
     
         14 . A method for manufacturing a perpendicular magnetic recording medium according to  claim 11 , wherein a temperature of the substrate in the step of forming the magnetic recording layer is lower or equal to 400° C.